LONDON — Carlos Alcaraz, locked in a five-set struggle at Centre Court, looked toward his coach Monday and shouted something about how Fabio Fognini — 38, retiring after this season, winless in 2025 — looked as if he could keep playing until he’s 50.

“I don’t know why it’s his last Wimbledon,” Alcaraz said later, “because the level he has shown, he can still play three or four more years. Unbelievable.”

The two-time defending champion at the All England Club needed to go through more than 4 1/2 hours of back-and-forth shifts against the much-older and much-less-accomplished Fognini before emerging with a 7-5, 6-7 (5), 7-5, 2-6, 6-1 victory in the first round.

It wasn’t supposed to be that tough.

Consider, to begin with, that the No. 2-seeded Alcaraz is 22, already a five-time Grand Slam champion, including his latest at the French Open three weeks ago, and is currently on a career-best 19-match winning streak.

Consider, too, that Fognini has never been past the third round at the All England Club in 15 appearances and reached the quarterfinals at any major tournament just once — way back at the 2011 French Open.

He entered Monday ranked 138th and 0-6 this year.

Oh, and then there’s this: Only twice has the reigning men’s champion at Wimbledon been beaten in the first round the following year, Lleyton Hewitt in 2003 and Manuel Santana in 1967.

There were times Monday when Alcaraz appeared to be something less than his best, far from the form he displayed during his epic five-set, 5 1/2-hour comeback victory over No. 1 Jannik Sinner for the championship at Roland-Garros.

Alcaraz double-faulted nine times. He faced a hard-to-believe 21 break points.

He made more unforced errors, 62, than winners, 52.

He chalked some of that up to nerves.

“Playing the first match at Centre Court, and the first match of every tournament, is never easy,” said Alcaraz, who beat Novak Djokovic in the 2023 and 2024 finals at that arena. “I’ve been practicing pretty well. I’ve been playing on grass really well. But Wimbledon is special. It’s different.”

Next for Alcaraz will be a match Wednesday against Oliver Tarvet, a 21-year-old British qualifier who plays college tennis at the University of San Diego and is ranked 733rd.

Still, Alcaraz said: “I have to improve in the next round.”

While Alcaraz escaped, at least five seeded men exited on Day 1, including No. 8 Holger Rune, No. 9 Daniil Medvedev — who also lost in the first round at the French Open — No. 16 Francisco Cerundolo, No. 20 Alexei Popyrin and No. 24 Stefanos Tsitsipas, who quit because of a persistent lower-back problem after dropping the first two sets.

No. 20 Jelena Ostapenko, the 2017 French Open champ, lost, while women’s winners included No. 1 Aryna Sabalenka, 2023 Wimbledon winner Marketa Vondrousova and 2021 U.S. Open champion Emma Raducanu.